Effects on the Atmosphere and Climate

The Creation of Heat Islands

Cities are made of concrete, asphalt, brick, stone, and steel. These materials absorb and reflect energy differently than vegetation and soil. They absorb more radiant energy and radiate this energy back into the atmosphere at different times through the day. The result is that cities are warmer than the surrounding countryside, sometimes considerably. Furthermore, cities remain warm well into the night when the countryside has already cooled. This heat influences air currents and patterns of precipitation. The two diagrams below illustrate the variations in temperature between urban and rural environments.

after Douglas 1983, 39

adapted from Detwyler 1971, 136

created 3/9/2002; last revised 5/1/2002 - Matt Kuhn & Andreas von der Dunk